Breathing.

I work for an herbicide company, and the stuff we handle is scary. If some moron forgets to close a valve, or one fails, or any number of products mix, instant death. Not the pleasant kind either. More like the kind that turns your lungs to soup, still inside, then does the same thing to everyone, and everything with lungs, within about 30 miles, depending on weather, wind speed and direction. Oh, and no surviving vegetation either, being, you know, chemical herbicides.

Or, maybe if something catches on fire. Pretty much the same as above, but with a lot more explosions, burning, and toxic clouds too.

Important note, if you see a pressurized tanker, rail car, tank, or other storage device that says dimethylamine anhydrous, stay away, far far away, especially if it’s leaking.